Migration Behaviour of Fission Products in CANDU Fuel

Abstract

A novel out-reactor method has been developed over the past few years for investigating the migration behaviour of fission products in oxide nuclear fuels, which allows the effects of thermal diffusion, radiation damage and local segregation to be independently assessed. Changes in tailored fission-product distributions that have been created in the near-surface region of polished wafers by ion implantation are precisely determined by depth profiling with high-performance secondary ion mass spectrometry (SIMS). This provides a direct measurement of the diffusive spreading of a well-defined source, which has generally been recognized as the only reliable approach for determining diffusion coefficients. Although bombardment with high-energy ions has been successfully used to simulate radiation-induced diffusion, the focus here will be on the effect of thermal diffusion.